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EP-3972438-B1 - HELMET IMPACT ATTENUATION LINER

EP3972438B1EP 3972438 B1EP3972438 B1EP 3972438B1EP-3972438-B1

Inventors

  • FRIEDER, LEONARD PETER, JR.
  • WEBER, JOHN B.
  • MATHEW, BIJU
  • CASPE, Russell J.

Dates

Publication Date
20260513
Application Date
20200520

Claims (13)

  1. An impact attenuation liner for a helmet (200) comprising: an additively manufactured lattice structure (102) configured to be disposed inside the helmet (200), the lattice structure (102) including a plurality of cells (104), each having a plurality of struts (106) and nodes (111), wherein the lattice structure (102) includes a top surface (107) having a convex curvature corresponding to an inner surface of the helmet (200) and a bottom surface (109) having a concave curvature configured to receive a user's head; characterized in that the additively manufactured lattice structure (102) is at least partially comprised of a 3D kagome lattice structure that includes a plurality of layers (114), each layer (114) having the plurality of cells (104); wherein the plurality of cells (104) of each layer of the plurality of layers has a geometry resembling a parallelepiped resembling tetrahedrons and hexagonal prisms arranged such that each side face of the hexagonal prism is shared with a face of an adjacent tetrahedron.
  2. The impact attenuation liner of claim 1 wherein a cross-sectional view of cells of the 3D kagome lattice structure shows each hexagonal prism including six tetrahedrons disposed around the perimeter of the hexagonal prism.
  3. The impact attenuation liner of claim 2 wherein the six tetrahedrons are connected at their vertices such that each tetrahedron has another tetrahedron connected at each of its vertices.
  4. The impact attenuation liner of claim 1 further comprising a 3D structure (300) disposed at least partially within the lattice structure (102); wherein the 3D structure (300) optionally comprises a different material than the lattice structure, the 3D structure (300) optionally being an aluminum honeycomb sheet.
  5. The impact attenuation liner of claim 1 further comprising a 3D structure (300) disposed at least partially within the lattice structure (102), wherein the lattice structure (102) includes a plurality of extending portions (120) and the 3D structure (300) includes a plurality of openings (302) each configured to receive one of the plurality of extending portions (120).
  6. The impact attenuation liner of claim 1 further comprising: a stiffening layer coupled to an outer surface of the lattice structure (102), the stiffening layer configured to function as at least a part of a shell of the helmet (200); wherein optionally the stiffening layer has a thickness ranging from 0.051 mm (0.020 in) to 2.54 mm (0.100 in) and an elastic modulus ranging from 0.5 GPa to 200 GPa.
  7. The impact attenuation liner of claim 1 further comprising: a stiffening intermediate layer disposed between the lattice structure (102) and one or more of an outer shell of the helmet (200) and a user's head, wherein the stiffening intermediate layer has an elastic modulus of approximately 0.5 GPa to approximately 200 GPa.
  8. The impact attenuation liner of claim 1, wherein: i) the additively manufactured lattice structure (102) comprises a macroscopic cross-linked carbon nanotube structure; or ii) the additively manufactured lattice structure (102) comprises a macroscopic cross-linked carbon nanotube structure with re-entrant angles;. or iii) the additively manufactured lattice structure (102) comprises an auxetic macroscopic cross-linked carbon nanotube structure.
  9. The impact attenuation liner of claim 1, wherein: i) the additively manufactured lattice structure (102) is comprised of polyurethane; or ii) the lattice structure (102) is at least partially comprised of a polymer where the polymer is comprised of one or more of polyurethane, polyamide, glass reinforced composites, carbon reinforced composites, thermoplastic polymer such as acrylonitrile butadiene styrene (ABS), polycarbonate, polyetherimide (PEI), polyetheretherketone (PEEK), thermoset polymer, acrylic polyurethanes, methacrylic polyurethanes, polyurea, polyacrylates, polymethacrylates and polyepoxides; or iii) the additively manufactured lattice structure (102) is comprised of a material configured to deform non-elastically; or iv) the additively manufactured lattice structure (102) comprises a plurality of lattice pads, each of the plurality of lattice pads comprised of an additively manufactured lattice.
  10. The impact attenuation liner of claim 1, wherein: i) the plurality of cells (104) each have a size between approximately 1 mm and approximately 30 mm; or ii) a ratio between a thickness of one of the plurality of struts (106) and a size of one of the plurality of cells (104) is between 1:4 and 1:120 and a ratio between the thickness of the one of the plurality of struts (106) and a length of one of the plurality of struts (106) is between 1:1 and 1:60.
  11. The impact attenuation liner of claim 1, wherein: i) the lattice structure (102) is configured to attenuate impact in response to an impact event having a velocity greater than approximately 3.0 m/s; or ii) the lattice structure (102) is configured to attenuate impact in response to an impact event having an energy level greater than approximately 47 J (35 ft-lb); or iii) the lattice structure (102) includes a first region having a first level of stiffness and a second region having a second level of stiffness different than the first level of stiffness to provide a different level of impact attenuation than the first region; or iv) the lattice structure (102) includes auxetic cell geometries with re-entrant angles ranging from approximately 180 degrees to approximately 270 degrees; or v) the lattice structure (102) includes a continuous network of channels (115) to enable management of power and data cabling through the lattice structure (102).
  12. The impact attenuation liner of claim 1, wherein the plurality of cells (104) have a plurality of struts (106) that are hollow and a plurality of nodes (111) that are hollow.
  13. A helmet system comprising: a helmet (200); an additively manufactured impact attenuation lattice structure (102) disposed within the helmet (200), the additively manufactured impact attenuation lattice structure (102) comprising: a top surface (107) having a convex curvature coupled to an inner surface of the helmet (200) and a bottom surface (109) having a concave curvature configured to receive a user's head; a plurality of cells (104) having a lattice geometry, the plurality of cells (104) having a plurality of struts (106) and nodes (111), wherein the plurality of cells (104) and the plurality of struts (106) are comprised of generally rigid polyurethane; and a continuous network of channels (115) disposed throughout the additively manufactured lattice structure (102), the continuous network of channels (115) configured to enable air to flow through the additively manufactured lattice structure (102); and a plurality of comfort pads (202) comprised of foam and coupled to an interior surface of the lattice structure (102), wherein the lattice structure (102) includes a first region having a first level of stiffness and a second region having a second level of stiffness different than the first level of stiffness to provide a different level of impact attenuation than the first region; wherein the additively manufactured lattice structure (102) is at least partially comprised of a 3D kagome lattice structure that includes a plurality of layers (114), each layer (114) having the plurality of cells (104); wherein each layer of the plurality of layers has a geometry resembling a parallelepiped resembling tetrahedrons and hexagonal prisms arranged such that each side face of the hexagonal prism is shared with a face of an adjacent tetrahedron.

Description

FIELD OF THE INVENTION The present invention generally relates to helmet liners having an additively manufactured lattice structure for impact attenuation. BACKGROUND OF THE INVENTION Helmet manufacturers have long dealt with the competing requirements of increased impact performance requirements and lower weight targets. Helmets typically have a rigid shell and a compressible liner disposed within the rigid shell. The compressible liner absorbs impact energy and reduces the amount of energy transferred to the user's head during an impact. Current technologies for helmet liners are typically foam based and have a homogenous impact profile. Due to the temperature dependence of existing liner materials, the impact performance is limited to the lowest common denominator over the expected operating range, i.e. lowest temperature, lowest impact velocity and energy. The tendency of foam padding to retain moisture and lack breathability, also leads to reduced user comfort during extended use. Further, the homogeneity of existing liner technology often leads to tradeoffs in performance in different regions of the liner and helmet, and prevents optimal performance with respect to weight. GB2490894 relates to a layer adapted for use in personal protection equipment such as a helmet or body armour. The layer includes a three-dimensional lattice structure formed of fused powder material. BRIEF SUMMARY OF THE INVENTION According to the appended claims, there is an impact attenuation liner for a helmet including an additively manufactured lattice structure configured to be disposed inside the helmet, the lattice structure including a plurality of cells, each having a plurality of struts and nodes, wherein the lattice structure includes a top surface having a convex curvature corresponding to an inner surface of helmet and a bottom surface having a concave curvature configured to receive a user's head. The additively manufactured lattice structure is at least partially comprised of a 3D kagome lattice structure. The 3D kagome lattice structure includes a plurality of layers, each layer having the plurality of cells. Each of the plurality of cells of the 3D kagome lattice structure has a geometry resembling a parallelepiped. Each of the plurality of cells may include vertices and at least one vertex is coupled to a tetrahedron. In some embodiments, the impact attenuation liner further includes a 3D structure disposed at least partially within the lattice structure. The 3D structure may comprise a different material than the lattice structure. The lattice structure may include a plurality of extending portions and the 3D structure includes a plurality of openings each configured to receive one of the plurality of extending portions. The 3D structure may be an aluminum honeycomb sheet. In some embodiments, the additively manufactured lattice structure comprises a plurality of lattice pads, each of the plurality of lattice pads comprised of an additively manufactured lattice. In some embodiments, the additively manufactured lattice structure comprises a macroscopic cross-linked carbon nanotube structure. In some embodiments, the additively manufactured lattice structure comprises a macroscopic cross-linked carbon nanotube structure with re-entrant angles. In some embodiments, the additively manufactured lattice structure comprises an auxetic macroscopic cross-linked carbon nanotube structure. In some embodiments, the additively manufactured lattice structure is comprised of polyurethane. The lattice structure may be at least partially comprised of a polymer where the polymer is comprised of one or more of polyurethane, polyamide, glass reinforced composites, carbon reinforced composites, thermoplastic polymer such as acrylonitrile butadiene styrene (ABS), polycarbonate, polyetherimide (PEI), polyetheretherketone (PEEK), thermoset polymer, acrylic polyurethanes, methacrylic polyurethanes, polyurea, polyacrylates, polymethacrylates and polyepoxides. In some embodiments, in the additively manufactured lattice structure comprised of a material configured to deform non-elastically. In some embodiments, the plurality of cells each have a size between approximately 1 mm and approximately 30 mm. In some embodiments, a ratio between a thickness of one of the plurality of struts and a size of one of the plurality of cells is between 1:4 and 1:120 and a ratio between the thickness of the one of the plurality of struts and a length of one of the plurality of struts is between 1:1 and 1:60. In some embodiments, the lattice structure is configured to attenuate impact in response to an impact event having a velocity greater than approximately 3.0 m/s. In some embodiments, the lattice structure is configured to attenuate impact in response to an impact event having an energy level greater than approximately 47 J (35 ft-lb). In some embodiments, the lattice structure includes a first region having a first level of stiffness and a second regio